INVERT's 'fwhm' and 'robust' parameters play well together?

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INVERT's 'fwhm' and 'robust' parameters play well together?

Postby and460 » Thu Aug 08, 2013 4:57 am

Hi guys,

I want to make a series of images at a whole bunch of different frequencies, but with the same final resolution. To date, I had been imaging with robust = -2, then cleaning, restoring, primary beam correcting and, finally, using CONVOL to convolve to the desired resolution.

It struck me that a nicer way to do this perhaps would just be to use the 'fwhm' parameter in INVERT to obtain the desired resolution in the images from the outset. However, since this effectively applies a visibility weighting scheme on the data, I was worried how this might 'play' together with my use of the robust weighting scheme. In other words, I was worried that I was applying two separate weighting schemes to the visibilities simultaneously, and that this might produce unpredictable results.

I was hoping you might be able to weigh in on whether or not this is a bad idea.

Cheers,
Craig.
and460
 
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Re: INVERT's 'fwhm' and 'robust' parameters play well togeth

Postby Mark.Wieringa » Thu Aug 08, 2013 10:11 am

Hi Craig,

no, I think it is perfectly reasonable to use both weighting schemes - the robust weighting modifies uniform weighting so there are no points with excessive weight causing extra noise or sidelobes and the gaussian taper just multiplies into those weights giving the same effect convol would have.
You may need to experiment a bit with the fwhm values to get the output beam size you want, as both robust weighting and tapering change the beam size.

Cheers,

Mark
Mark.Wieringa
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